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OBDII Code P0451- Evaporative Emission Control System

qck

:
Mazda 2011 CX-9 GT FWD
OBDII Code P0451 MAZDA - Fuel Tank Pressure Sensor Malfunction

Three days ago the CEL came on when I started the vehicle up leaving for work. The CX-9 ran fine and is still running fine today from what I can tell just a driver. I went to an auto parts place nearby yesterday and got the code looked up for free and it is P0451: http://engine-codes.com/p0451_mazda.html I ordered a Scan Gauge II two days ago and should have it sometime next week. I'm on the fence as to should I take it in to the dealer or wait until my scan gauge comes in and reset the code with it and then see if it comes back. It is a 2011 and has 22,500 miles on it.

Has anyone else ever have this code come up and if so what did you do about it?
 
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2017 Mazda CX-5 GT, 2016 Mazda6 iGT, 2014 Mazda3 sGT hatchback
Seems like fuel pump problem to me.
The fuel pump is inside the fuel tank.
ScanGauge cannot tell you more than what you know.
You can reset the code with it, but you might be stranded if you don't get it looked at since it is still under OE warranty.
Good Luck.
 
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2011 CX-9
definitely take it in if it's under warranty. always good to have those issues documented in case it becomes a problem down the line.
 

helbigtw

T-Rav
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PA
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08 CX-9 GT FWD
I agree. Definately get the dealer to look at it rather than just clearing the code to avoid any warranty problems down the road if you fail to mitigate the issue.
 

qck

:
Mazda 2011 CX-9 GT FWD
I took it to my dealer and the problem is the fuel tank pressure sensor had been shorted. I recently (one week before this happened) had my vehicle undercoated and they said this is what caused the problem. Sensor is roughly $145, $95 for the diagnostic check and labor is $50 to replace. Final total is $292, which is twice as much as my undercoating cost me.

Are the sensor plugs not suppose to be sealed to prevent this?
 
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2017 Mazda CX-5 GT, 2016 Mazda6 iGT, 2014 Mazda3 sGT hatchback
Shouldn't you contact the guy who did undercoating to pay for it?
If there is hard evidence, that is.
 

qck

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Mazda 2011 CX-9 GT FWD
Yes I had the dealer note it on the invoice, and I will contact the place I had it done at.
 
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2007 Mazda CX 9
Problem with PO451 also.

I have a 2007 CX 9 that has the PO451 code. I checked the connection at the fuel tank pressure sensor and it was ok. Should I replace the sensor or could it be something else that is setting the code.
 
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2007 Mazda CX 9
On the CX 9 it is on a hose coming from the back of the fuel tank. It's easy to get to, I was just checking to see if it could have been something else that set the code before I replace it.
 

damaster

Zoom Zoomin'
:
2011 CX-9 GT
I took it to my dealer and the problem is the fuel tank pressure sensor had been shorted. I recently (one week before this happened) had my vehicle undercoated and they said this is what caused the problem. Sensor is roughly $145, $95 for the diagnostic check and labor is $50 to replace. Final total is $292, which is twice as much as my undercoating cost me.

Are the sensor plugs not suppose to be sealed to prevent this?
Same problem here and had to pay $90 for the CEL check even though I had already checked it myself and had known the code was P0451. They told me it was the undercoating and they cleaned the sensor for me. CEL came back a few days later and I'm back at the dealer now.

I've had many, many cars undercoated by the same rust proofing shop and this is the first time this has ever happened. Seems like Mazda really didn't do a good job protecting the sensor on the CX-9.
 

damaster

Zoom Zoomin'
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2011 CX-9 GT
My P0451 came back and I think the fuel tank pressure sensor is f'd up again. Does anyone know exactly where it is and what it looks like?
 
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2011 CX-9 GS
Can the sensor be cleaned (and maybe seal it better) or will it need to be replaced? I am in the same boat. just undercoated a new to me 2011 CX-9. It is running ok, but is throwing the same code.
 
G

Guest2018

Three days ago the CEL came on when I started the vehicle up leaving for work. The CX-9 ran fine and is still running fine today from what I can tell just a driver. I went to an auto parts place nearby yesterday and got the code looked up for free and it is P0451: http://engine-codes.com/p0451_mazda.html I ordered a Scan Gauge II two days ago and should have it sometime next week. I'm on the fence as to should I take it in to the dealer or wait until my scan gauge comes in and reset the code with it and then see if it comes back. It is a 2011 and has 22,500 miles on it.
Intermittent nature indicates a failure in progress. Wires and connectors love to fail intermittently before their final complete failure. Not uncommon. No one can diagnose without having your vehicle but based solely upon what you just indicated as a symptom, it could be time to replace the Fuel Tank Pressure Sensor which is physically going to be attached to the fuel tank itself. Or, it could be something as simple as you leaving the fuel cap improperly sealed after your last fill up at the gas station by accident and the EVAP system 'detects' that as vacuum leak (though you make no reference to DTC P0446 which is common for EVAP Vent System Failures).

With P0451, the very first thing you can check on your own is the fuel cap - is it properly sealed. Sometimes the fuel cap is properly sealed but just worn out and needs to be replaced - especially if it has a history of not being secured or sealed properly. There have been reports of people simply replacing their fuel cap and disappearing the check engine light along with P0451.

1) Remove and re-seal fuel cap
2) Delete P0451 using your Scan Tool

If the code does not return, you have more than likely solved the problem. If the code returns, you obviously have more troubleshooting to do.


Your FTP sensor has three wires. One of those wires sends a reference voltage signal to the ECU/ECM (typically up to 5 volts) which it uses to function the EVAP monitor (your FTP is part of your EVAP system). That wire, or one of the other two remaining wires (5v wire or Ground Wire) could be bad, but you would need to conduct a proper voltage test to determine this. The FTP sensor is also connected to your fuel tank via hose as well and it should be checked for cracks and wear. A Seal & Purge Test may need to be run on your tank which checks the EVAP Solenoid and FTP sensor function - whether or not they are working together properly. Electrical circuit function to and from the FTP sensor and EVAP Solenoid would be revealed as well as EVAP Solenoid valve function. Something your mechanic will probably have to do - unless you have or obtain the right Scan Tool and are willing to learn how to use it to initiate the troubleshooting sequence.

I don't know where the FTP sensor is located on your vehicle exactly, but if you can reach it without dropping the tank it would be possible for you to learn how to run your own voltage diagnostic on the unit using a simple multi-meter. If you don't feel comfortable learning how to do that, or can't reach the unit given its location, then taking it to certified/trained/experienced mechanic is probably no doubt the best thing to do.

It is great that you at least pulled the code - took the right first step. That gives you a basic or general reference on the starting point for solving the problem and it enables you to at least talk with your mechanic about it. This unit should not effect drive-ability. That's why you got a DTC without problems from the vehicle. At the same time, you don't know of the other components within the EVAP system are causing this particular DTC to emerge suddenly.

Run the fuel tank cap check. That's the easiest thing you can check on your own. Report back if you can. I'd like to know how this turned out for you.
 
G

Guest2018

Seems like fuel pump problem to me.
The fuel pump is inside the fuel tank.
ScanGauge cannot tell you more than what you know.
You can reset the code with it, but you might be stranded if you don't get it looked at since it is still under OE warranty.
Good Luck.

If he had a fuel pump problem, then that would negatively impact drive-ability at some point and I would expect to see some problems at engine idle or an outright crank-no-start condition. What do you think?
 
G

Guest2018

I took it to my dealer and the problem is the fuel tank pressure sensor had been shorted.
I should have read further along in the thread before making my first post. Sounds about right based on your reported symptoms.

Glad you got it fixed! :)
 
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2010 CX-9 GT
Just got this code the other day, after my wife filled the gas tank. Thought it might be gas cap related, but after several days with a new gas cap, the "check engine" light has not extinguished.

The part # for the fuel tank pressure sensor is TE69-42-58X (I think). Confusingly, the part title is "Evaporative Hose with Sensor". If the check engine light remains on, I will probably have a go at replacing this hose assembly and seeing if that fixes the issue. It looks pretty easy to do, I was just hoping the gas cap would fix it...
 
:
2010 CX-9 GT
Just got this code the other day, after my wife filled the gas tank. Thought it might be gas cap related, but after several days with a new gas cap, the "check engine" light has not extinguished.

The part # for the fuel tank pressure sensor is TE69-42-58X (I think). Confusingly, the part title is "Evaporative Hose with Sensor". If the check engine light remains on, I will probably have a go at replacing this hose assembly and seeing if that fixes the issue. It looks pretty easy to do, I was just hoping the gas cap would fix it...
Updating in case others have this issue...

I replaced the "Evaporative Hose with Sensor" part listed above (TE69-42-58X). No more Check Engine light. The part was ~$85 through an online parts supplier. It is a 10 minute job, the part is really easy to swap - all you need is a flat blade screwdriver to get the "quick release" connectors off.
 
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2011 Mazda CX-9 Touring
Updating in case others have this issue...

I replaced the "Evaporative Hose with Sensor" part listed above (TE69-42-58X). No more Check Engine light. The part was ~$85 through an online parts supplier. It is a 10 minute job, the part is really easy to swap - all you need is a flat blade screwdriver to get the "quick release" connectors off.
Where is it at?

I'm getting this code and looking to do this too. I replaced my fuel cap with a new one and the code popped back up.
 
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2010 CX-9 GT
Where is it at?

I'm getting this code and looking to do this too. I replaced my fuel cap with a new one and the code popped back up.
This part is attached to the fuel tank, but you don't have to drop the tank or anything to get to it. The fuel tank is under the second row seats, and this part is attached to the side of the fuel tank that faces towards the rear of the car. You can get to it by crawling under the car near the left rear wheel and looking up.

I attached a photo - the rear of the car is toward the bottom of the picture. The fuel tank is just out of the frame at the top of the photo. For reference, the larger black tube on the left of the photo is the fuel filler and it runs back to the fuel door. The part you want to replace is the U-shaped black tube that runs from the top center of the photo, through the white clip, and then bends around and attaches to the tube on the right side of the photo. The pressure sensor is the bit right in the middle of the photo with the wires attached - there's no way to replace this by itself, you have to buy the whole tube assembly and replace it.
 

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